Coastal Rivers Aquatic Vegetation Analysis
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Coastal Aquatic Vegetation Analysis Weeki Wachee, Chassahowitzka, and Homosassa Coastal Rivers Aquatic Vegetation Analysis For Weeki Wachee, Chassahowitzka, and Homosassa Rivers August 2016 Coastal Aquatic Vegetation Analysis Weeki Wachee, Chassahowitzka, and Homosassa Table of Contents Executive Summary 1 1.0 Introduction 1-1 2.0 Scope of Project 2-1 3.0 Methods 3-1 3.1 Study Area 3-1 3.1.1 Regional Description 3-1 3.1.2 River Descriptions 3-3 4.0 Sampling Methods and Analytical Procedures 4-1 4.1 Submersed Aquatic Vegetation 4-1 4.1.1 Weeki Wachee River 4-1 4.1.2 Chassahowitzka River 4-4 4.1.3 Homosassa River 4-5 4.2 Quality Assurance, Data Summaries and Statistical Analyses 4-7 5.0 Results and Discussion 5-1 5.1 Total SAV Coverage 5-1 5.2 Total Vegetative Biomass 5-2 5.3 Angiosperm Biomass 5-5 5.4 Macroalgal Biomass 5-9 6.0 Analysis of Distributional and Biomass Changes 6-1 6.1 Discussion of Statistical Methods 6-1 6.2 Weeki Wachee River 6-3 6.2.1 Description of the Data 6-4 6.2.2 Overview of Statistical Procedures 6-7 6.2.3 Comparison of the 2015 Data and the Historical Data for the Weeki Wachee River 6-7 6.2.4 Discussion of Results 6-14 6.3 Chassahowitzka River 6-16 6.3.1 Description of the Data 6-17 6.3.2 Overview of Statistical Procedures 6-20 6.3.3 Comparison of the 2015 Data and the Historical Data from the Chassahowitzka River 6-20 6.3.4 Discussion of Results 6-28 6.4 Homosassa River 6-30 6.4.1 Description of the Data 6-31 6.4.2 Overview of Statistical Procedures 6-35 6.4.3 Comparison of the 2015 Data and the Historical Data 6-35 6.4.4 Discussion of Results 6-42 GNV/2016/152803A/8/6/15 i Coastal Aquatic Vegetation Analysis Weeki Wachee, Chassahowitzka, and Homosassa 6.5 Inter-River Comparisons 6-44 6.5.1 Description of the Collected Data and the Analyses 6-44 6.5.2 Comparison of the Data by Sampling Events for All Three Rivers 6-45 6.5.3 Comparison of the 2015 SAV Data to Pooled Data from Previous Sampling Events 6-50 6.5.4 Changes in SAV Data over Time 6-52 6.5.5 Discussion and Conclusions 6-59 7.0 Concluding Remarks 7-1 8.0 Literature Cited 8-1 Appendices Appendix A – Field data sheets for the 2015 monitoring period Appendix B – Submersed aquatic vegetation data collected for the period of record (CD attached) Appendix C – Period of record results –SAV coverage, SAV biomass, angiosperm biomass and macroalgae biomass Appendix D -- Frequency of occurrence and distributional patterns Appendix E – Results of SAS© statistical significance testing Appendix E1 – Weeki Wachee River Analysis Appendices: Results of SAS© Statistical Significance Testing Appendix E2 – Chassahowitzka River Analysis Appendices: Results of SAS© Statistical Significance Testing Appendix E3 – Homosassa River Analysis Appendices: Results of SAS© Statistical Significance Testing GNV/2016/152803A/8/6/15 ii Coastal Aquatic Vegetation Analysis Weeki Wachee, Chassahowitzka, and Homosassa List of Tables Table 4-1. Middle Station Location (latitude-longitude) for Weeki Wachee River Transects Sampled during the 2015 Monitoring Event ........................................................ 4-2 Table 4-2. Middle Station Location (latitude-longitude) for Chassahowitzka River Transects Sampled during the 2015 Monitoring Event ........................................................ 4-5 Table 4-3. Middle Station Location (latitude-longitude) for Homosassa River Transects Sampled during the 2015 Monitoring Event ........................................................ 4-7 Table 6-1. River-Wide Mean Total SAV Biomass for the Weeki Wachee River for All Previous Years (combined) Compared to the Mean Total SAV Biomass for 2015. .................................................................................................................. 6-8 Table 6-2. Comparison of Total SAV Biomass for the Weeki Wachee River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due to small biomass values. .................................................................................... 6-9 Table 6-3. River-Wide Mean SAV Percent Cover for the Weeki Wachee River for 2003- 2011 (combined) Compared to the Mean Total SAV Percent Cover for 2015. .. 6-10 Table 6-4. Comparison of Total SAV Percent Cover Data for the Weeki Wachee River by Transect for 2003-2011 (combined) and for 2015 ............................................. 6-10 Table 6-5. River-Wide Change in Mean Angiosperm Biomass for the Weeki Wachee River for All Previous Years (combined) Compared to the Mean Angiosperm Biomass for 2015. ............................................................................................ 6-12 Table 6-6. Comparison of Angiosperm Biomass for the Weeki Wachee River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due to small biomass values. ........................................................................... 6-12 Table 6-7. River-Wide Change in Mean Macroalgae Biomass for the Weeki Wachee River for All Previous Years (combined) Compared to the Mean Macroalgae Biomass for 2015. Additional significant figures shown due to small biomass values............................................................................................................... 6-13 Table 6-8. Change in Macroalgae Biomass for the Weeki Wachee River by Transect as Measured by the Difference between the Macroalgae Biomass for All Previous Years (combined) Compared to the Macroalgae Biomass for 2015 and the percentage of increase or decrease ................................................................. 6-13 Table 6-9. River-Wide Mean Total SAV Biomass for the Chassahowitzka River for All Previous Years (combined) Compared to the Mean Total SAV Biomass for 2015. ................................................................................................................ 6-21 Table 6-10. Comparison of Total SAV Biomass (gm/m2) for the Chassahowitzka River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due to small biomass values. ..................................................... 6-22 Table 6-11. River-Wide Mean SAV Percent Cover for the Chassahowitzka River for 2003- 2011 (combined) Compared to the Mean Total SAV Percent Cover for 2015. .. 6-23 Table 6-12. Comparison of Percent SAV Cover Data for the Chassahowitzka River by Transect for 2003-2011 (combined) and for 2015 ............................................. 6-24 GNV/2016/152803A/8/6/15 iii Coastal Aquatic Vegetation Analysis Weeki Wachee, Chassahowitzka, and Homosassa Table 6-13. River-Wide Change in Mean Angiosperm Biomass for the Chassahowitzka River for All Previous Years (combined) Compared to the Mean Angiosperm Biomass for 2015. ............................................................................................ 6-24 Table 6-14. Comparison of Angiosperm Biomass for the Chassahowitzka River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due to small biomass values. ..................................................... 6-25 Table 6-15. River-Wide Change in Mean Macroalgae Biomass for the Chassahowitzka River for All Previous Years (combined) Compared to the Mean Macroalgae Biomass for 2015. ............................................................................................ 6-26 Table 6-16. Change in Macroalgae Biomass for the Chassahowitzka River by Transect as Measured by the Difference between the Macroalgae Biomass for All Previous Years (combined) compared to the macroalgae biomass for 2015 and the percentage of increase or decrease ................................................................. 6-27 Table 6-17. River-Wide Change in Mean Total SAV Biomass for the Homosassa River for All Previous Years (combined) Compared to the Mean Total SAV Biomass for 2015. Additional significant figures shown due to small biomass values. .......... 6-37 Table 6-18. Comparison of Mean Total SAV Biomass (gm/m2) for the Homosassa River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due to small biomass values ...................................................... 6-37 Table 6-19. River-Wide Mean SAV Percent Cover for the Homosassa River for 2003-2011 (combined) Compared to the Mean Total SAV Percent Cover for 2015. ........... 6-38 Table 6-20. River-Wide Mean SAV Percent Cover for the Homosassa River for 2003-2011 (combined) Compared to the Mean Total SAV Percent Cover for 2015. ........... 6-38 Table 6-21. River-Wide Change in Mean Angiosperm Biomass for the Homosassa River for All Previous Years (combined) Compared to the Mean Angiosperm Biomass for 2015. Additional significant figures shown due to small biomass values............................................................................................................... 6-40 Table 6-22. Comparison of Angiosperm Biomass for the Homosassa River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due to small biomass values. .................................................................................. 6-40 Table 6-23. Comparison of Macroalgae Biomass for the Homosassa River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due to small biomass values. .................................................................................. 6-41 Table 6-24. Comparison of Macroalgae Biomass for the Homosassa River by Transect for 1998-2011 (combined) and for 2015. Additional significant figures shown due